This invention relates generally to manually actuated torue magnifying wrenches and more particularly to the bearing supports for the inertia member of these wrenches.
Manually actuated torque magnifying wrenches permit the user to store energy in a spring which is released to provide a momentary torque far in excess of what the human operator could have achieved with a standard wrench of the same dimensions.
Several patents have been issued on manually actuated impact tools for applying a torsional force, greater than applied to the tool at the moment of torsional force application. This includes U.S. Pat. Nos. 2,661,647; 2,884,982; 2,954,714; 3,108,506; 3,156,309, 4,382,476; and 4,418,768.
In each of these patents, the operation of the device illustrates a manually operable impact tool. Each device generally contains a manually operable handle, a power spring for the momentary storage of energy, and an annular inertia member carrying pawls which engage a ratchet-toothed member. The ratchet-toothed member is connected to the output shaft which is connectable to a socket or other mechanism to engage a threaded fastener such as a nut or bolt.
Energy derived from the movement of the handle is stored in and is released by the power spring. At the moment of release, the annular inertia member forces its pawls into the ratchet-toothed member to cause the ratchet-toothed member to rotate, thereby either rotating or attempting to rotate the output shaft to either loosen or tighten the threaded fastener.
In this manner, the operator is able to store up energy in the power spring for later momentary application. This results in a force being applied to the threaded fastener which is far in excess of that which could be applied by the same dimensional wrench by the same operator.
Although the tools of the above patents have proven superior in performance to traditional tools, the energy which is released from the power spring has caused problems which heretofore were corrected by the addition of strengthening material which in turn creates a tool which is heavier and less desirable to use.
Specifically, with regards to the tools of U.S. Pat. Nos. 4,382,476, and 4,418,768, the inertia member is maintained in position through the use of a bearing being extended from the frame member. The frame members therefore must be able to withstand the shock of the power when the power spring releases, necessitating undesirable increase in their weight to withstand this shock.
Additionally, in the construction of these tools, the annular inertia member is supported between the frame members by a bearing surface at the inner surface of the annular inertia member mating with a bearing surface attached to each frame member. Because of this design, the diameter of these bearing surfaces is relatively large with respect to the overall diameter of the inertia member. Since loss of torque output from the tool due to friction in these bearing surfaces is proportional to their diameter, these tools have an inordinate amount of friction energy loss.
As with all hand tools, the weight of the tool is critical and must be maintained so that the operator can use it in hard to reach places and can readily transport it from the field vehicle to the work location.